The present invention relates to organic semiconductors and to the use thereof in organic electronic devices.
Organic semiconductors are being developed for a number of different applications which can be ascribed to the electronics industry in the broadest sense. The structure of organic electroluminescent devices (OLEDs) in which these organic semiconductors are employed as functional materials is described, for example, in U.S. Pat. No. 4,539,507, U.S. Pat. No. 5,151,629, EP 0676461 and WO 98/27136. However, these devices still exhibit considerable problems which require urgent improvement:    1. Many dopants in accordance with the prior art are only accessible in complex multistage synthetic methods.    2. The lifetime of the organic electroluminescent devices in accordance with the prior art is still inadequate for high-quality applications.    3. The thermal stability, in particular of many blue dopants, is inadequate.    4. Many compounds, in particular blue dopants, in accordance with the prior art have high sensitivity to oxygen and light, which makes synthesis and handling thereof considerably more difficult.
Prior art which may be mentioned in the case of blue-emitting compounds is the use of arylvinylamines (for example WO 04/013073, WO 04/016575, WO 04/018587). However, these compounds are thermally unstable and cannot be evaporated without decomposition, which requires high technical complexity for OLED production and thus represents an industrial disadvantage. A further disadvantage is the emission colour of these compounds: while dark-blue emission (CIE y coordinates in the range 0.15-0.18) is described in the prior art with these compounds, it has not been possible to reproduce these colour coordinates in simple devices in accordance with the prior art. Green-blue emission is obtained here. It is not apparent how blue emission can be generated with these compounds.
Also known as blue and green emitters in accordance with the prior art are aromatic diamines with condensed aromatic compounds, for example with anthracene, pyrene or chrysene (WO 04/078872, EP 1437395, WO 04/044088). However, these likewise do not have satisfactory properties in the device, in particular with respect to the lifetime, but also with respect to the operating voltage. Furthermore, these compounds are very sensitive to oxygen and light, which makes handling thereof more difficult, in particular on an industrial scale.
There therefore continues to be a demand for improved materials, in particular blue-emitting compounds, which are thermally stable, result in good efficiencies and at the same time in long lifetimes in organic electronic devices, give reproducible results during the production and operation of the device and are readily accessible synthetically.